Return flow carburetor



March 31, 1964 T. M. BALL RETURN FLOW CARBURETOR original Filed'June 5,1959V /a Uf JNVENTOR.

United States Patent O 3,127,454 RETURN FLGW CARBURETOR Thomas M. Ball,Bloomfield Hills, Mich., assigner to Chrysler Corporation, HighlandPark, Mich., a corporation of Delaware Original application .lune 5,1959, Ser. No. 318,349, now Patent No. 3,098,885, dated July 23, 1963.Divided and this application Mar. 23, 1961, Ser. No. 97,775 Claims. (Cl.261-36) This invention relates to improvements in a carburetorparticularly adapted for use with -an automobile internal combustionengine `and is a division of my copending application Serial No.818,349, tiled June 5, 1959, new Patent No. 3,098,885.

In conventional carburet-ors, .a float controlled fuel inlet needlevalve is employed to regulate the fuel level in the carburetor fuelbowl. Small dirt particles sometimes interfere with effective operationof the valve, as for example by becoming lodged between mating valveseats which otherwise cooperate to regulate the fuel ilow into the fuelbowl. Also the floats require considerabie size in order to be`effective because o-f the companatively lo-w specific gravity of thefuel. In consequence the size of the fuel bowl must be appreciablylarger than is otherwise desired.

An important object of the present invention is to provide an improvedcarburetor which avoids the foregoing objections and `in particular toprovide a fioatless carburetor which does not require a fuel inletneedle valve.

Another object is to provide such a construction including ,an overllowstandpipe in the fuel bowl having an upper opening Iwhich determines themaximum fuel level in the bowl. A fuel inlet pump is provided to pumpfuel into the bowl at a rate in `excess of demand. The excess fueloverllows into the standpipe and is returned to the fuel tank. ln orderto overcome `adverse grade conditions which prevent the excess fuel fromreturning to the tank by gravity flow, a scavenging pump is provided inthe fuel return line between the overflow standpipe and the tank.

Among other advantages of the above structure, elimination of thenecessarily large fioat enables utilization of a comparatively smallfuel bowl closely adjacent the inlet air induction conduits of amultiple barrel carburetor, for example, The small fuel bowl thuslocated is less sensitive to grade and inertial effects and enablesuniform fuel distribution to each of the several induction conduits.Also recirculation of the fuel drives off its more volatile fuelfractions and thereby minimizes some of the problems of the conventionalfioat controlled carburetor, as for example those concerned with vaporformation.

ln order to provide adequate fuel during maximum engine speed at wideopen throttle, a fuel inlet pump is provided Iwhich delivers an excesssupply of fuel to the fuel bowl during all operating conditions of theengine. When the throttle is suddenly closed while the engine is stilloperating at high speed, unless some provision is made to the contrary,`approximately 98% of the fuel supplied to the fuel bowl will berecirculated, whereas approximately only 2% of the fuel will be used bythe engine. ln general the life of a fuel pump and in particular thelife of an engine driven diaphragm type pump, which is preferred forsupplying fuel in the quantity required and at a substantially uniformpressure regardless of changes in engine speed, depends upon thequantity of fuel pumped.

For the above reasons, as well as the desirability of conserving powerin an automobile engine and of minimizing fuel heating by excessiverecirculation, another object of the present invention is to provideimproved simple and highly effective means for supplying fuel to thefuel bowl in reasonable and safe amounts related to engine requirements.

Another object is to provide a bypass conduit which extends from thedischarge side of the fuel supply pump to the inlet side of the pump andwhich contains a suitable valve adjustable -in response to variations inengine load for controlling the fuel flow in the bypass conduit.

Other and more specific objects are to adjust the bypass control valveby a `direct linkage with the throttle actuating mechanism.

Other objects of this invention will appear in the following descriptionand `appended claims, reference being had to the accompanying drawingforming a part of this specioation wherein like reference charactersdesignate corresponding parts in the single view.

The figure is a schematic mid-sectional view of a return flow carburetorand pump embodying the present invention.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

Referring to the figure, `the carburetor shown comprises a cast housingforme-d to provide an air inlet induction conduit including a venturiportion 10 having a restricted venturi 111 at its upper portion and athrottle blade 12 pivotally mounted on a shaft 13 at a lower portionusually referred to as the throttle body. An upper portion of thecasting is formed to provide an air horn 14 adapted to be connected withthe usual air lter and opening at its downstream end into the venturi 11to supply air thereto. The casting portions 10 and 1'4 are suitablysecured together, as for example by screws not shown, and comprise anupper portion of the air inlet and fuel mixing induction -system whichextends downstream of the throttle valve i12; and discharges into theusual engine cylinders in a conventional manner.

Integral with the casting 10 in the present instance is a fuel bowlcasting 115 containing an annular chamber or fuel bowl `lo enclosing acylindrical standpipe or weir 17 which also serves as an `accelerationpump cylinder containing a plunger 1S reciprocable in its lower portionand secured to a plunger Ishaft 1'9 for actuation thereby. Where desiredthe shaft 19 is connected by suitable linktage with a pedal operatedaccelerator mechanism which controls the opening and closing of valve 12to operate conjointly therewith. 'Upon upward movement of plunger 13,fuel is drawn into the lower portion of chamber 17 via conduit 20 incommunication with the bowl 16. A suitable check valve illustratedschematically as a ball check element Z1 nonmally seats at the mouth ofthe duct 20 opening into the lower portion of chamber 17 to pre-ventloss cf fuel therefrom but is raised from its seat by tbe fuel flow intochamber 17 on the upstroke of plunger 18. Upon downward movement ofplunger 118 the fuel is forced from chamber 17 into the inductionconduit via yacceleration fuel conduit I2.2, ball check valve 23, landnozzle 4 which latter discharges into the induction conduit at alocation immediately above the throat of venturi 11. The check valve 23is schematically illustrated as a ball normally urged by a spring to aseated position closing nozzle 24 from the interior of chamber 17, theball being readily movable upward against the tension of its seatingspring by the acceleration fuel pressure upon downward movement ofplunger 18. The main fuel to the engine is supplied via duct 25 whichopens a-t its lower end through metering port 26 into the fuel bowl 16and communicates at its upper end with a fuel nozzle 27 hav-ing itsdit-charge orifice located Within the thro-at of venturi 1-1.

In accordance with the structure described thus far, fuel entering thebowl 16 in excess of engine requirements overflows the upper edge ofstandpipe 17 which thereby maintains the fuel in the bowl 16 at apredetermined maximum level determined by the effective height of thestandpipe y17 without recourse to a float operated mechanism. Fuel issupplied to the bowl16 from a suitable fuel tank -28b via conduit 28.

A multiple piece fuel pump housing 37 comprising an upper dome 38 and alower basin 39 cooperate with diaphragms 40 and 41 respectively toprovide an inlet fuel pumping or working chamber 42 and an exhaust fuelpumping or scavenging chamber 43. Springs 44 and 45 under compressionbetween portions of housing 37 and diaphragms 40 and 41 respectivelyurge the former diaphragm upwardly and the latter diaphragm downwardlyto effect the pumping strokes for the respective chambers 42 and 43.

The upper working chamber 42 comprises a portion of supply duct 2S whichcommunicates upstream of chamber 42 with the fuel tank. Fuel enters andleaves chamber 42 via an inlet port 46 and a discharge port 47associated with check valves 48 yand 429 respectively. Upon downwardmovement of diaphragm 41B as explained below, fuel is drawn in thedirection of the arrow 28a from the tank and through inlet port 46 intoworking cham-ber 42. During this operation ball valve 48 is forced fromits seat at port 46 by the fuel flow, and ball valve 49 seats at thedischarge port `47 to close the latter from the fuel bowl 16. Uponupward movement of diaphragm 40, ball valve 48 is caused to` seat atport 46 to close the Working chamber 42 from the fuel tank. During thisoperation, the pressure exerted in chamber 42 unseats ball valve 49 fromport l47 and supplies fuel via conduit 28 to the fuel bowl 16. Thespaces at the sides ofthe diaphragms 40 and 41 opposite chambers 42 and43 respectively are vented to the atmosphere by ducts 50' and 51 tofacilitate the pump operation.

In order to prevent too great an excess of fuel from being pumped tobowl 116 when the engine 4is operating at comparatively light load, abypass conduit 42a is provided which communicates at opposite ends withthe discharge and inlet sides of chamber 42 respectively at locationsdownstream of port 47 and upstream of port 46. A valving port or orifice29 in conduit 42a is controlled by a tapered needle valve 76 registeringwith port 29 at the latters high pressure side. Upon downward movementof valve 76, orifice 29 is progressively restricted to reduce the fuelflow therethrough as described below.

Fuel is returned in the direction of arrow 52a from standpipe 17 to thefuel tank 23b via fuel return conduit 52 which includes chamber 43 as aportion thereof. Inasmuc-h as fuel return conduit 52 in cooperation withfuel tank 21811 and a portion of inlet conduit 28 return the overflowfuel from standpipe 17 to the inlet side of pumping chamber 42, thethree elements co-mprising conduit 52, fuel tank 28h, and the portion ofconduit 2S upstream of pumping chamber 42 may be considered part of thefuel return system or means. Upstream, the conduit 52 communicates withstandpipe 17 at a location above the uppermost limit rof movement ofplunger 18. The return fuel enters chamber 43 via port 53 and dischargesfrom chamber 43 via port 54. Ball check valves 55 and 56 are associatedwith ports 53 and 54 respectively, so that upon upward movement ofdiaphragm 41 as described below, ball 56 seats against port 54 to closechamber 43 from the fuel tank. During this operation, ball 55 isunse-ated from port 53 to open communication between chamber 43 andstandpipe '17 and to draw fuel from the latter. Upon downward movementof diaphragm 41, ball 55 is seated against port 53 to close chamber 43from standpipe 17. Simultaneously ball 56 is unseated from port 54 bythe pressure in chamber 43 to discharge fuel from the latter in thedirection of arrow 52a to the tank. Movement limiting pins in theconduits 23 and 52 associated with the ball valves 48, 49, 55 and 56prevent undue movement of the balls from their associated ports.inasmuch as the check 'valves are well known, these are merely shownschematically and are not discussed in further detail.

Actuation of the diaphragms 40 and 41 is accomplished by driving shafts57 and 58 connected to these diaphr-agms and terminating yin enlargedheads 59 and 60 respectively. Pivotal levers 61 and 62 are pivoted onhousing 37 at locations '63 and 64 respectively between their ends. Eachlever has one end engaged with a rotating eccentric cam' 65 mounted on-a shaft 66 driven by the automobile en gine. The opposite ends of thelevers 61 and 62 are pro-y vided with oversized openings 67 and 68through which the rods 57 and 58 extend freely to enable their relativesliding movement with respect to the levers 61 and 62 until the leversengage the enlarged heads 59 and 60.

Upon operation of the automobile engine, shaft 66 is rotated to turneccentric cam 65 and thereby cause pivot,- ing of levers 61 and `62.Upon clockwise pivoting of lever 61, or counterclockw'ise pivoting oflever 62, the head 59 or 60 is engaged to pull the associated rod 57 and58 in the direction to compress the spring 44 and 45 as the case mightbe. Upon counterclockwise pivoting of lever 61 and clockwise pivoting oflever 62, the oversized openings 67 and 68 enable the levers to swingindependently of the shafts 57 and '58, whereupon springs 44 and 45 arereleased to force diaphragms 40 and -41 in pumping actions toward theassociated dome 38 or basin 39. The pivotal action of levers 61 and 62merely compresses the springs 44 and 45 alternately, which latter thenexert resilient force to effect the pumping action of the associateddiaphragms 40 and 41. In consequence, fuel is discharged from chamber 42at a uniform optimum pressure determined by the force of spring 44. Uponthe upward spring urged pumping stroke of diaphragm 40, fuel isdischarged via port 47 to fuel bowl 16. All fuel in excess of enginerequirements overflows the standpipe 17 and returns by conduit 52tochamber 43 via port 53, whereupon the fuel is pumped to the fuel tankby downward spring urged pumping movement of diaphragm 41.

The restriction of orifice 29 is controlled by a mechanid cal linkagewith the throttle valve mechanism. A valve actuating stem 77 secured tovalve 76 extends upwardly therefrom and through a housing 75 and isyieldingly urged downwardly by a coil spring 78 under compression aroundstem 77 between a portion of housing 75 and a spring retaining seat 79suitably secured to stem 77. The latter extends upwardly and is freelyslidable through an oversized hole 80 in a dog-leg bracket 81 andterminates in an enlarged head 82 which is unable to pass throughopening 80. Bracket 81 is secured to the upper horizontal portion of adog-leg lever 83 having a vertical depending portion. A connecting linkS4 is pivotally connected at 85 to the lower depending portion of lever83 and is also pivotally connected at 86 to the outer swinging end of acrankarm 87 which in turn is keyed to an extension of valve shaft 13exteriorly of the induction conduit 10.

Upon pivoting of crankarm 87 as for example by linkage S8 suitablyconnected with crankarm 87 and the customary pedal operated throttlemechanism, valve 12 is opened or closed. Upon clockwise pivoting ofcrankarm 87, throttle valve 12 is progressively opened and lever 83y ismoved downwardly, causing bracket 81 to slide down wardly freely alongvalve stem 77 and enabling spring 78` to force stem '77 and valve 76downwardly to increase the restriction at orifice 29. In consequenceupon opening of the throttle valve 12 during increased engine load,bypass fuel flow through orifice 29 is decreased and fuel flow to bowl16 is increased. Upon counterclockwise orl closing movement of valve 12with decreasing engine load, lever 83 is moved upwardly. Bracket 81 thenengages the enlarged head 82 and raises stem 77 against the force ofspring 78 Valve 76 then progressively opens orifice 29, increasing thebypass fuel fiow in conduit 42a and reducing the fuel flow to bowl 16.In this regard the resistance to fuel flow in conduit 28 downstream ofbypass conduit 42a is preferably greater than the correspondingresistance in bypass conduit 42a and is predetermined, as for example bya restricted orifice 30, in order to assure adequate fluid flow inbypass conduit 42a when Valve 76 opens.

Having thus described my invention, I claim:

l. In a carburetor for an internal combustion engine having a fuel andair induction system, a floatless fuel bowl, duct means connecting saidbowl and system for supplying fuel to the latter, a fuel pump having aninlet adapted to be connected with a source of fuel and also having anoutlet, inlet conduit means connecting said outlet and fuel bowl forsupplying fuel to the latter upon operation of said pump, means formaintaining the fuel in said bowl at a predetermined level comprising anoverflow Weir in said bowl defining at least in part a chamber adaptedto receive excess fuel overflowing said weir from said bowl when thefuel in said bowl attains said predetermined level, fuel return means incommunication with said chamber to drain fuel therefrom upon overfiow ofexcess fuel from said bowl into said chamber, a bypass duct connectingsaid inlet with said inlet conduit means at a location downstream ofsaid outlet, means for prorating the fuel flow from said outlet to saidfuel bowl and bypass duct including valve means in said bypass duct forcontrolling the fuel flow therein and thereby to control the fuel flowto said bowl, control means including a throttle valve in said systemfor controlling the air flow therein, and means operably connecting saidcontrol means and valve means for adjusting the latter in accordancewith operation of said throttle valve to increase the fuel flow in saidinlet conduit means to said fuel bowl with opening of said throttlevalve.

2. In a carburetor for an internal combustion engine having a fuel andair induction system, a throttle valve in said system, a floatless fuelbowl, duct means connecting said bowl and system, a fuel pump, having aninlet and an outlet, first conduit means connecting said outlet withsaid fuel bowl for supplying fuel to the latter upon operation of saidpump, means for maintaining the fuel in said bowl at a predeterminedlevel comprising an overflow weir in said bowl defining at least in parta chamber adapted to receive excess fuel overflowing said weir from saidbowl when the fuel in said bowl attains said predetermined level, fuelreturn means for returning excess fuel from said chamber to said inletincluding a fuel return conduit in communication with said chamber todrain fuel therefrom upon overflow of excess fuel thereinto from saidbowl, means for diverting a portion of the fuel in said first conduitmeans from said fuel bowl and system including bypass conduit meansconnecting said first conduit means with said fuel return means, meansfor proportioning the fuel flow from said fuel pump to said bowl andbypass conduit means including a predetermined restriction in said rstconduit means at a location between said bowl and the connection of saidbypass conduit means with said first conduit means, said means forproportioning also including valve means in said bypass conduit meansfor controlling fuel fiow in the latter, and means responsive to engineload for adjusting said valve means comprising an operable linkageconnecting said throttle valve and valve means.

3. In a carburetor for an internal combustion engine having a fuel andair induction system, a throttle valve in said system, a fioatless fuelbowl, duct means connecting said bowl and system, a fuel pump having aninlet and an outlet, first conduit means connecting said outlet withsaid fuel bowl for supplying fuel to the latter upon operation of saidpump, means for maintaining the fuel in said bowl at a predeterminedlevel comprising an overflow Weir in said bowl defining at least in parta chamber adapted to receive excess fuel overflowing said Weir from saidbowl when the fuel in said bowl attains said predetermined level, fuelreturn means for returning excess fuel from said chamber to said inletincluding a fuel return conduit in communication with said chamber todrain fuel therefrom upon overiiow of excess fuel thereinto from saidbowl, means for diverting a portion of the fuel in said first conduitmeans from said fuel bowl and system including bypass conduit meansconnecting said first conduit means with said fuel return means, meansfor proportioning the fuel flow from said fuel pump to said bowl andbypass conduit means including a predetermined restriction in said firstconduit means at a location between said bowl and the connection of saidbypass conduit means with said first conduit means, said means forproportioning also including valve means in said bypass conduit meansfor controlling fuel flow in the latter, and means responsive to engineload for adjusting said valve means comprising an operable linkageconnecting said throttle valve and valve means to decrease the fuel flowin said bypass conduit means progressively upon progressive opening ofsaid throttle Valve.

4. In a carburetor for an internal combustion engine having a fuel andair induction system, a throttle valve in said system, a fioatless fuelbowl, duct means connecting said bowl and system, a fuel pump having aninlet and an outlet, first conduit means connecting said outlet withsaid fuel bowl for supplying fuel to the latter upon operation of saidpump, means for maintaining the fuel in said bowl at a predeterminedlevel comprising an overflow Weir in said bowl defining at least in parta chamber adapted to receive excess fuel overflowing said Weir from saidbowl when the fuel in said bowl attains said predetermined level, fuelreturn means for returning excess fuel from said chamber to said inletincluding a fuel return conduit in communication with said chamber todrain fuel therefrom upon overflow of excess fuel thereinto from saidbowl, means for diverting a portion of the fuel in said first conduitmeans from said fuel bowl and system including bypass conduit meansconnecting Said first conduit means with said fuel return means, meansfor proportioning the fuel flow from said fuel pump to said bowl andbypass conduit means including a predetermined restriction in said firstconduit means at a location between said bowl and the connection of saidbypass conduit means with said first conduit means, said means forproportioning also including valve means in said bypass conduit meansfor controlling fuel fiow in the latter, means responsive to engine loadfor adjusting said valve means comprising an operable linkage connectingsaid throttle valve and valve means, said linkage including actuatingmeans movable in one direction for actuating said valve means todecrease the fuel flow in said bypass conduit means progressively withprogressive opening of said throttle valve, and resilient meansassisting movement of said actuating means in said one direction.

5. In a carburetor for an internal combustion engine having a fuel andair induction system, a throttle valve in said system, a oatless fuelbowl, duct means connecting said bowl and system, a fuel pump having aninlet and an outlet, first conduit means connecting said outlet withsaid fuel bowl for supplying fuel to the latter upon operation of saidpump, means for maintaining the fuel in said bowl at a predeterminedlevel comprising an overfiow weir in said bowl defining at least in parta chamber adapted to receive excess fuel overflowing said Weir from saidbowl when the fuel in said bowl attains said predetermined level, fuelreturn means for returning excess fuel from said chamber to said inletincluding a fuel return conduit in communication with said chamber todrain fuel therefrom upon overflow of excess fuel thereinto from saidbowl and also including return fuel pumping means operable insynchronism with said fuel pump, means for diverting 'a portion of thefuel in said first conduit means from said fuel bowl and systemincluding by- `pass conduit means connecting said rst conduit means withsaid fuel return means, means for proportioning the fuel ow from saidfuel pump to said bowl and bypass conduit means including apredetermined restriction in said rst conduit means at a locationbetween said bowl and the connection of said bypass conduit means withsaid rst conduit means, said means for proportioning also includingmetering valve means in said bypass conduit means for controlling fuelow in the latter, means responsive to engine load for adjusting saidvalve means comprising an operable linkage connecting said throttlevalve and valve means, said linkage including actuating lmeans movablein one direction for actuating said valve meansY to decrease the fuelliow in said bypass conduit means progressively with progressive openingof said throttle valve, and resilient means assisting movement of saidactuating means in said one direction.

References Cited in the file of this patent UNITED STATES PATENTS f

1. IN A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE HAVING A FUEL ANDAIR INDUCTION SYSTEM, A FLOATLESS FUEL BOWL, DUCT MEANS CONNECTING SAIDBOWL AND SYSTEM FOR SUPPLYING FUEL TO THE LATTER, A FUEL PUMP HAVING ANINLET ADAPTED TO BE CONNECTED WITH A SOURCE OF FUEL AND ALSO HAVING ANOUTLET, INLET CONDUIT MEANS CONNECTING SAID OUTLET AND FUEL BOWL FORSUPPLYING FUEL TO THE LATTER UPON OPERATION OF SAID PUMP, MEANS FORMAINTAINING THE FUEL IN SAID BOWL AT A PREDETERMINED LEVEL COMPRISING ANOVERFLOW WEIR IN SAID BOWL DEFINING AT LEAST IN PART A CHAMBER ADAPTEDTO RECEIVE EXCESS FUEL OVERFLOWING SAID WEIR FROM SAID BOWL WHEN THEFUEL IN SAID BOWL ATTAINS AID PREDETERMINED LEVEL, FUEL RETURN MEANS INCOMMUNICATION WITH SAID CHAMBER TO DRAIN FUEL THEREFROM UPON OVERFLOW OFEXCESS FUEL FROM SAID BOWL INTO SAID CHAMBER, A BYPASS DUCT CONNECTINGSAID INLET WITH SAID INLET CONDUIT MEANS AT A LOCATION DOWNSTREAM OFSAID OUTLET, MEANS FOR PRORATING THE FUEL FLOW FROM SAID OUTLET OT SAIDFUEL BOWL AND BYPASS DUCT INCLUDING VALVE MEANS IN SAID BYPASS DUCT FORCONTROLLING THE FUEL FLOW THEREIN AND THEREBY TO CONTROL THE FUEL FLOWTO SAID BOWL, CONTROL MEANS INCLUDING A THROTTLE VALVE IN SAID SYSTEMFOR CONTROLLING THE AIR FLOW THEREIN, AND MEANS OPERABLY CONNECTING SAIDCONTROL MEANS AND VALVE MEANS FOR ADJUSTING THE LATTER IN ACCORDANCEWITH OPERATION OF SAID THROTTLE VALVE TO INCREASE THE FUEL FLOW IN SAIDINLET CONDUIT MAEANS TO SAID FUEL BOWL WITH OPENING OF SAID THROTTLEVALVE.